The present invention relates to a method and a device for limiting the transverse acceleration of a traveling vehicle.
Vehicles such as off-road vehicles or minibuses are driven to an increasing extent which have a very good road contact (i.e. traction), on the one hand, and a comparatively high center of gravity, on the other hand. This may cause problems inasmuch as the transverse forces which are transmitted due to the good road contact are of so great an amount that the resulting centrifugal force causes the vehicle to tilt. The physical relationship will be explained briefly by way of FIG. 2.
The embodiment of FIG. 2 shows schematically the rear of a vehicle 210 on a road surface 200. Reference numerals 103 and 104 represent the wheels on the rear axle. It shall be assumed that the vehicle drives in a right bend, that is, would move to the right in a projection to the drawing plane. Due to the vehicle driving on a circular course, a centrifugal force Z=mxc2x7xcfx892xc2x7r=mv2/r is produced, with m being the vehicle mass, o being the angular velocity in the circular course, v being the vehicle speed and r the radius of the circular course. The centrifugal force Z that acts and may be expressed as the product aq.m, with aq being the transverse acceleration, may be considered as acting upon the point of gravity S of the vehicle. The point of gravity S is disposed roughly centrically between the wheels and at a height h above the road surface. Also, the weight force G=mxc2x7g acts upon the point of gravity S, with g being the acceleration due to gravity. As long as the vehicle drives on the desired circle (aq=v2/r then applies), that is as long as the cornering forces F on the four wheels (approximately corresponding to F=xcexcxc2x7G, with xcexc being the coefficient of friction between tires and road surface) are equal to the centrifugal force Z, the mentioned centrifugal forces will be produced according to the above equation. It may happen in this case that the vehicle rolls over the outward wheel due to an unfavorable distribution of torques. This will principally happen when Gxc2x7b/2 less than Zxc2x7h applies, with h being the level of the point of gravity S above the road surface 200 and b/2 being roughly half the track width of the vehicle. The above unbalanced equation represents in a first approximation the torque balance around point P. When the outward turning torque Zxc2x7h is greater than the inwards turning torque Gxc2x7b/2, the vehicle will tilt outwards. This risk is especially imminent in vehicles having a small track width (b/2 small) and a comparatively great height and, thus, a high point of gravity (great value of h), e.g. due to a roof load 220 on vehicle 210.
In order to be able to avoid such an operating condition, it is necessary
to detect a critical situation, especially a driving condition with a critical transverse acceleration, and
to take appropriate countermeasures after the detection.
An object of the present invention is to provide a simple and reliable method and a corresponding device for limiting the transverse acceleration of a traveling vehicle.